Orthodontic model former



June 28, 1938. A. J. OLIVER ORTHODONTIC MODEL FORMER Filed May 29, 1937 SECTIONS-3 INVENTOR. 0 M J W ATTORNEY.

Patented June 28, 1938 UNITED STATES PATENT OFFICE 3 Claims.

In orthodontic and other dental practice, it is customary to give the surplus parts of the two separate casts respectively reproducing the teeth of the upper and lower jaws a standardized form when finished, with the top surface of the cast representing the upper jaw and the corresponding bottom surface of the cast representing the lower jaw carefully made plane and parallel with the line of occlusion of the teeth, and with the lateral edges of such surplus parts trimmed on planes perpendicular to such finished top and bottom surfaces so as to give both casts an identical hexagonal shape in plan which approximates a triangle with its corners cut off. This is done both to impart a neat and finished aspect to the finished cast, and to facilitate correct correlation in the course of subsequent study and measurement in the course of orthodontic procedure, the making of dentures, and related work.

Since these casts must be made in relatively hard and unyielding plastics such as plaster of Paris, artificial stone, and other calcareous materials, the problem of cutting the casts quickly and accurately into the desired shape and imparting thereto a smooth finished appearance has led to many and varying resorts in the manner of moulding, cutting and grinding the exterior surfaces of the casts. Such resorts have for various reasons left considerable room for improvement.

Accordingly, it is the aim of the invention to provide a novel and improved method and device for finishing the casts used in orthodontic and other dental practice, which shall have advantages in making easier and simpler the process of finishing such casts, while imparting thereto a superior finish, and, most important of all, shall permit the finishing of both halves of a model simultaneously, to have identical'shape, without breaking the points of the teeth through vibration when held in articulated relation during the operation.

To this end, the invention comprises in its fundamental aspects the provision of a rotary grinding, cutting, or planing tool, and guiding surfaces for the work associated with such tool in adjustable manner, whereby the depth, direction, and angularity of the cutting or planing action is at all times under accurate and micrometric control and the attainment of truly plane surfaces is assured.

Other objects of the invention, and the manner in which they are attained, are as set forth hereinafter.

An illustrative embodiment of the invention is shown in the accompanying drawing, in which Fig. 1 is a plan view, and Fig. 2 a side elevation, of the improved device of the invention.

Fig. 3 is a vertical section on line 3-3 of Fig. 1, looking in the direction of the arrows.

Fig. 4 is a diagram of the manner of forming the cutting flutes on the cutting tool.

Fig. 5 is a plan view of a cast of the teeth of a lower jaw, showing the finished shape imparted thereto through the use of the device of the invention.

Fig. 6 is a front elevation of the two halves of a model, comprising casts of matching upper and lower j aws, to act in articulated relation after having been cut to identical contour through the use of the invention.

Having reference to the drawing- The base I of the machine is in the form of a hollow closed box, adapted to be secured to a bench or other support by fastenings put through the lugs 2 at the four corners thereof. One end of thebox is cut off along an oblique plane intersecting the top of the box along a line extending across the top at right angles at about midlength of the top of the box, such plane also intersecting the end of the box along a horizontal line slightly abovethe bottom of one end, and on rails or rabbets 3 formed inside the box along the oblique edges of this end of the box slide the correspondingly rabbeted edges 40 of a separate piece I5, rectangular in plan and in end elevation and triangular in side elevation, supplying the otherwise missing corner of the box. This movable portion cooperates with a fixed portion 24 fixed to the side walls I3 by screws 42, to form'the bed of the planer.

At midlength of such bed is the cutting tool 4, comprising a shaft of tool steel having its intermediate portions fluted or otherwise shaped to effect the desired type of cutting or planing action. It is mounted for high speed rotation in self-lubricating bushings 5 fixed in bearings 6, 6, self-lubricating thrust-washers i being interposed betweenv the annular recess atthe end of each bearing and a collar 8 fixed to each end of the shaft by a clamping screw. The tool is rotated directly by a V-pulley 36'fixed on the protruding end of the tool, such pulley being connected by a V-belt to a similar pulley on the armature shaft of an electric motor (not shown).

Provision is made for adjusting the elevation of the cutting tool with respect to the fixed bed 24 of the machine in the form of screws I I passing through lugs M on sides 53 of the base and equipped with nuts I0 and I2 above and below such lugs, the end of each screw being screwed tightly into a threaded recess in bearings 6; cap screws t6 threaded into the side Walls I3 through vertically elongated slots in lugs 48 on the bearings maintain the desired adjustment. This adjustment is for the accommodation of tools for various diameters, since all that is required is to keep the top of the tool level with the fixed bed 24.

The depth of cut is regulated by the relative elevation of the. top surfaceof the movable portion 55 comprising the other half of the bed of the planer. It is over the top surface of this portion l that the work is fed to the tool, and this top surface is raised or lowered while remaining ever parallel with the'fixed portion 24 of the bed by reason of its engagement on an oblique plane with the rabbets described.

An important feature of the invention is the provision for accurately controlling and adjusting the position of this movable part I5 of the feed table for adjusting the depth of cut. vThis comprises a lever Ha, pivoted on a screw 22 fixed in a web 56 extending across the interior of the base i from side to side and from the righthand end thereof to a point near the tool 4, parallel to and just below the rabbets 3. The lever 56 has near its inner end ,anobliquely-disposed cam slot 52, through which passes the unthreaded middle portion of a stud il in fixed screw-threaded engagement with a boss 56 on the center of the under side of the top portion of the part [5, this stud also passing through a slot in web 50 which is elongated lengthwise of the bed. An expanding coil spring i 8 surrounds the stud below the web, and is held under compression by washer l9 and nuts 20, 2i, whereby the movable portion it is held firmly against the rabbets 3 constituting its trackway. As is obvious, when the free end of lever I6 is swung to the right, the movable portion 55 of the bed will be slid along its track toward the tool it, with resultant raising of its work-supporting top surface with respect to the top of the tool, thereby reducing the depth of the cut made by the tool in work which is fed toward the tool while pressed manually firmly into contact with the top surface of the movable portion 45 ofthe bed. When the lever I6 is moved to the left, the cam slot 52 acts on the pin to move the movable portion down the incline, exposing an increased part of the circuit of the tool and lowering the plane of the top surface of portion 55 to increasethe depth of cut. Stop screws 23, threaded through the lever into the ends of the cam slot 52, provide adjustable means for limiting the throw of the lever and hence the scope of elevation of the movable bed 5 and of its movement toward and from the tool 4. The leverage thus obtained makes possible a very accurate setting of the elevation of portion I 5 and therefore of the depth of out.

To ensure and facilitate the trimming of the lateral edges of the cast on planes perpendicular to the finished top and bottom surfaces of the cast, in the process of giving the two parts an identical hexagonal shape, a sliding perpendicular guide or support for the work is provided. This comprises a vertical wall 27, in dove-tailed sliding engagement at the surfaces 56 with a vertical upturned flange 58 on a slide 26 in dove-tailed and horizontally sliding engagement with a rail 25 fixed by screws 6!! to the fixed bed 2 3 of the machine. The nature of this dove-tailed sliding engagement is indicated at 62 in Fig.3. Expanding coil springs 35 are confined in pockets in the vertical flange 58 of the slide 26, and engage horizontally extending lugs 64 on the top edge of the vertical wall of the guide or support 21. These springs serve to hold the work-guide or support 27 yieldingly lifted so that its lugs 64 are out of engagement with the top of the vertical flange 58 of slide 26. When fully depressed, the bottom edge of the work-guide 21 is still maintained above and clear of the rapidly rotating tool 4 by reason of engagement between the lug 64 and the top of vertical flange 58.

The advantage of making the work-guide 2'! verticallyyieldable within limits is that repeated cuts can be taken off of one side of the cast without having to shift the work downwardly with respect to the guide, and thus a perfectly plane surface can be achieved without any tendency to make a rounding out. Further, it can be made to serve as a depth gauge, if the primary position of the work against the guide is held.

After the top or bottom surface of the cast has been planed smooth, this plane surface is placed against the guide with the thumb of the operators right hand Within the semi-circle of the teeth and the palm and fingers of such hand engaging the top of the guide 21 and the back of the flange 58 of slide 26. After each cut, a slight relaxation of the downward pressure of the hand, without relaxing the grip, permits spring 35 to lift the guide and the work with it, so that during the idle retracting stroke of the guide and slide from left and right the work is held clear of the tool l and there is no likelihood of accidental contact which would knock off corners of the'cast at the advancing end of the out just made, since the tool rotates in a clockwise direction as viewed in Fig. 2. The succeeding cuts are made by simply depressing the guide until the workmeets the top surface of portion l5 of the bed, and then feeding the work to the tool by movement of the guide and slide from right to left along the track 25, still without relative shift of the work with respect to the guide 21. If the range or vertical travel of guide 2? is inadequate to effect the depth of cut desired, the grip of the thumb and the downward pressure of the hand is relaxed to let the work gravitate into conformity with either half of the bed of the machine, whereupon the work is again clamped to the guide by thumb pressure and the cutting resumed.

Mitering guides 29, 31, are provided in connection with the guide 21, having plane surfaces standing out at right angles to the vertical face of guide 21, and mounted for angular adjustment on the bed of the machine by means of their shanks 3|, which are screwed into hubs formed on these mitering guides and rotatably mounted in sleeves 28 fixed in the end portions of the guide 2?. The mitering guides are frictionally held in adjusted angular position by thumb nuts 3| on their shanks and engaging the rearward ends of sleeves 28, and certain predetermined angular relationships of these mitering guides to the bed of the machine are established by depressions 34 in the vertical face of guide 2'! which are engaged by a ball pressed thereinto by a spring 33 recessed into the opposing face of the mitering guides. Thus, after the first out of the edge of the cast has been made, this cut surface is placed in conformity with the proper one of the twomitering guides, (depending on whether the cast is that of the upper or lower jaw, if the two parts are being finished separately), while the previously planed top or bottom surface of the cast is still held against the vertical guideZ'l, and the second cut on the edge of the cast is made in the predetermined angular relation to the first of such cuts which define the outline of the finished cast. Since the improved device makes it possible for the two halves of a model to be planed when held together, without danger of chipping the teeth through chattering and vibration, an identical shape can be given to both halves, and a single guide only is needed. The several positions of the mitering guides provide for changes of angle to accommodate casts taken from long and narrow jaws as well as short and broad jaws.

Another feature of the invention resides in the construction of the cutting tool 4 itself.

The nature of the material being cut, plaster, artificial stone, and the like, has made it extremely difficult to find cutting means which would stay sharp long enough to justify their employment. I have found that a spiral fluted cutter' of relatively small diameter and of true cylindrical shape, having a large number of relatively fine flutes, and rotated at high speed, gives the best results and puts a uniform smooth surface free from tool marks on this material. In order to keep the tool from rapidly losing its cutting edge, I have also found that it is necessary to form the leading or cutting face of each flute with a backward rake, so that the angle between the radial portion of the flute and the original cylindrical exterior of the tool is slightly greater than a right angle. That is, a line tangent to the (nearly) radial face of the two surfaces which meet to form the cutting edge passes not through the axis of the tool, but slightly to one side thereof, as indicated in Fig. 4, the angle a indicating this divergence. Also, the cylindrical portion of each flute must be narrowed by relieving the back of the edge as indicated at B, and the groove C must be of liberal depth in order to avoid fouling to an extent clogging the tool.

A sliding tray It is provided in the bottom of the base i, to catch the material removed from the work by the action of the tool 4. With the base thus entirely enclosed, and a strip of leather 6B glued to the under side of the movable portion I5 of the bed between. the depending inner end of web 50 and the tool, to prevent the escape of dust down the web 50 and out through the slot under portion it across which lever 16 swings back and forth, the device is entirely dustless and dirt-free in its operation.

Through the use of the device of the invention an untrained operator can easily produce results of an accuracy and quality of finish hitherto unattainable by known means, and do so while cutting the two parts of a mouth model at once, without the customary risk of breaking the points of the teeth with resultant loss of the accuracy of the model. As a result, the two parts may be stood on edge upon a table or other plane supporting surface while preserving their accurate articulated relation, for observation or the taking of measurements.

While I have illustrated and described certain forms in which the invention may be embodied, I am aware that many modifications may be made therein by any person skilled in the art, without departing from the scope of the invention as expressed in the claims. Therefore, I do not wish to be limited to the particular forms shown, or to the details of construction thereof, but

What I do claim is:

1. In a machine tool of the character described, a rotating cutter, a bed supporting the work above the cutter and on which bed the work rests and slides, and a work-guide slidable with the work along the bed and across the cutter and mounted for up-and-down movement with respect to the bed.

2. In a machine tool of the character described, a rotating cutter, a bed supporting the work above the cutter and on which bed the work rests and sildes, and a work guide slidable with the work along the bed and across the cutter, to be grasped and propelled by the operators hand, and having an upright surface against which the work is held by the thumb of the said hand for movement in unison with the work-guide and yieldable downwardly under manual pressure to press the work against the bed without need for relative movement of the work with respect to the work-guide.

3. In a machine tool of the character described, a rotating cutter, a bed sup-porting the work above the cutter on which bed the work rests and slides, and a work-guide slidable with the work along the bed and across the cutter, and means yieldingly maintaining the work-guide in raised relation with respect to the bed with capacity for being manually depressed to press the work against the bed after successive cuts without shift of the work with respect to the work-guide.

ALFRED J. OLIVER. 

